Maximising transferred power and preserving zero voltage switching in grid to vehicle and vehicle to grid modes of a wireless charging system

Modelling of a wireless charging system for an electrical vehicle is one of the main challenges to control the system, optimally. Considering a suitable integrated model for both the vehicle and stationary sides is essential to guarantee the maximum power transfer in these systems. This study presents an analytical model of an inductive contactless charger, used for controlling the vehicle side of the system to transfer charging power and regenerative (vehicle to grid) power as high as possible. First, the system parameters are set based on the derived analytical model, then the settings are readjusted by a finite-element model as a fine tuning. The system is controlled in a way that soft switching in both the charging and regenerative modes is guaranteed. The under study system has 20 kW power with an inter-coil distance between 14 and 21 cm, and a bidirectional converter with series–series resonance compensation. The system is assessed in detail theoretically and the results are confirmed using some experiments carried out on a prototype in the same rating.